Multiple low doses of streptozotocin (mid sz 40 mg/kg/day, five consecutive days) induce autoimmune diabetes in mice. The aim of the present work was to study beta-cell function in mice injected with splenocytes from mid-sz diabetic mice. Mononuclear splenocytes (MS) from control or diabetic donors were injected into syngeneic C57BL/6J healthy mice (5 x 10(7) MS, ip). MS from diabetic donors did not produce basal hyperglycemia, but they induced abnormal ip glucose tolerance in recipient mice. These "diabetic" MS were also preferentially trapped by the recipient's pancreas. Perifused pancreas from mice injected with MS from mid sz-diabetic donors showed a diminished first and second phase of glucose-induced insulin secretion after 15 days of the cell injection. At this time, pancreatic insulin content among MS recipients did not differ from that found in controls or diabetic donors. Diabetic MS treated with Mitomycin C prior to transfer did not inhibit insulin secretion in recipient mice. Injection of MS from mice made diabetic by a single high sz dose (200 mg/kg) did not induce any alterations of the insulin secretion in recipients. There is enough evidence when using athymic and euthymic (BALB/c nu/nu and +/nu) mice to suggest that proliferation of the injected splenocytes enhanced the progression to the diabetic state, and that both donor and recipient T lymphocytes played an important part in this progression. The results suggest that injection of MS from mid sz-diabetic mice interfere with glucose-stimulated insulin secretion in recipient mice and provide a basis for the study of the mechanisms involved in the onset and modulation of autoimmune pancreatic aggression.

Etiological agents of autoimmune processes that have been made nonvirulent by several treatments, I.e., mitomycin C (Mit C), can be used as a vaccine to protect against disease. In this work we studied the effects of splenocytes from diabetic mice on animals that had been injected with modified splenocytes (Mit C-treated splenocytes from multiple low-dose streptozotocln [mld-sz] mice) 15 days before. Splenocytes from rnld-sz diabetic donors altered I.p. glucose tolerance and the first peak of Insulin secretion pattern when injected into normal singenelc recipients. These effects can be prevented partially (one Injection in a vaccine form) or completely (two injections with a 15day interval) by a previous injection of Mit C-treated mononuclear splenocytes (MS) from mld-sz mice. The fact that control splenocytes previously treated with Mit C were not able to achieve similar results Indicates that donor splenocytes have to be diabetic to prevent the disease. On the other hand, Mit Ctreated diabetic MS were not effective in preventing the alterations in glucose tolerance and in the pattern of insulin secretion when Injected Into athymlc mice. This suggests that the preventive effect of Mit C-treated diabetic MS Injection also Implies an active role of the T cells from the recipient mice. Mit C-treated diabetic splenocytes are preferentially trapped by the pancreas and the lymph nodes from recipient mice. Our results show that the impairment In glucose tolerance and In the insulin secretion pattern produced by diabetic splenocyte transfer can be prevented. by one or two previous injections of Mit Cmodified diabetic splenocytes.

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This work reports the effects of a previous injection of mitomycin-modified splenocytes from multiple-low dose streptozotocin-treated mice (mld-sz) on autoimmune diabetes produced by mld-sz. Our work shows that a previous inoculation of modified mononuclear splenocytes from mld-sz mice prevents alterations in glycemia, in insulin secretion (IS) pattern from isolated perifused islets, and in mass of pancreatic islets. Immunohistochemistry showed an alteration in the number of beta, but not of alpha or delta cells. While a mononuclear intra-islet infiltration was observed in mld-sz mice, a predominantly polar or peri-islet infiltration was seen in vaccinated mice. Islet-associated mononuclear cells from mld-sz mice produced diabetes and induced a diminished IS when transferred to normal receptors. Those cells from previously vaccinated mld-sz mice had no effect when injected into normal receptors. In addition, they also inhibited the damage induced in normal receptors by the islet-associated mononuclear cells from mld-sz animals. Cellular death was also prevented by previous vaccination. Our results suggest that vaccination with modified splenocytes from mld-sz mice is capable of shifting the islet cells infiltration pattern from an aggressive one toward a protective one and thus preventing the ß cell destruction observed in mld-sz mice.

Summary. In a previous study in C57BL/KsJ (mdb)mice aged 12 to 90 days, we observed alterations in the secretion of insulin and somatostatin and in the inhibitory effect of the latter upon insulin secretion. This study explores whether hormonal alterations are to be found in the very early stages of the diabetic syndrome, i.e. between ages 4 and 12 days. The results demonstrate two distinct phases in the development of the syndrome: (a) up to age 6 days, the perifused slices of pancreata of control animals present bilShasic glucose-induced patterns of insulin and somatostatin secretion, whereas the diabetic animals show a diminished first peak of insulin secretion, but a similar pattern of somatostatin secretion, to that of the control animals; Co) between ages 7 and 12 days, the pancreata of diabetic mice exhibit insulin hypersecretion in basal conditions, and an absence of the first secretion peak and insulin hypersecretion in the second phase in response to glucose stimulation. The glucose-induced pattern of somatostatin secretion presents hormonal hypersecretion in both phases. Bcell sensitivity to the inhibitory effect of somatostatin is diminished in mdb mice of the above-mentioned groups, an alteration which becomes more evident as diabetes evolves. The results show that, in very early stages of the evolution of the diabetic syndrome in C57BL/KsJ (mdb) mice, there are already alterations in insulin and somatostatin secretion patterns and in the inhibitory effect of the latter on insulin secretion. In a previous study [4] on C57BL/KsJ (db/db) mice aged 12 to 90 days, we observed: a) basal and glucosestimulated insulin hypersecretion, with absence of the first secretion peak; b) somatostatin secretion patterns showing hormonal hyper-, normo-and hyposecretion, together with altered secretion dynamics; and c) diminished B-cell sensitivity to the inhibitory effect of somatostatin, which gradually became more noticeable as animals grew older. Key words:Considering these results, we have investigated whether the above-mentioned alterations occur in very early stages (ages 4 to 12 days), or whether they are to be found during the later evolution of the diabetic syndrome in C57BL/KsJ-mdb mice. Normal homozygous and heterozygous carriers (% + + / + + and mdb/+ + genotypes) aged 4 to 12 days were used as controls and were designated as lean mice. It is necessary when using these groups as control, to know if this genotypically heterogenous population is a homogeneous one regarding insulin and somatostatin secretion. A test to determine variance equality (homoscedasticity) between the control group and the mutant group and between the control group and BALB/c mice was done. BALB/c mice were chosen because they are a genotypically population free of known deletereous mutations. Homoscedasticity did not allow the detection of an heterogeneous composition in our control group. Materials and methods Animal model Experimental models of the pancreas Incubation of pancreas slices. The technique described by Martin andBamber...